1. Field of Invention
The present invention relates generally to lawn maintenance devices, and, more particularly, to lawn maintenance devices that can perform more than one task such as mowing, trimming and edging and can be easily changed from one mode of operation to another.
2. Description of Prior Art
In lawn maintenance, the three conventional operations are: (i) general lawn cutting; (ii) trimming areas near fences, buildings and the like; and (iii) edging to make a sharp edge along a walkway, driveway or the like. These three operations are conventionally, respectively performed on three different machines. For general lawn cutting, a gasoline powered push or riding mower is conventionally used. For trimming, a hand-held electric or gasoline powered filament line lawn trimmer is used. For edging, an electric or gasoline powered edge trimmer with a vertical metal blade is used. The use of three separate devices drives cost requirements and storage space requirements. The use of three separate devices also consumes time required for comprehensive lawn maintenance as the operator switches from one device to the next for the three operations set forth above. The hand-held line trimmer can be fatiguing to use for extended periods. The three machines are also often difficult to control properly, resulting in gouging of turf. The high required blade speed can result in damage to tree bark and to paint on fences and buildings. Also, if gasoline powered, the heavy vibration that results from using a hand-held trimmer can cause “hand-arm vibration syndrome” if the device is used for long periods. Finally, line trimmers cut by mashing the top of grass, rather than by making a clean cut. This mashing action can cause browning of grass tops. Filament line trimmers are often unusable in vegetation more robust than grass. Traditional edgers with vertical metal blades can cause damage to driveways and walkways if proper care and/or attention is not given.
Numerous attempts have been made to reduce the fatigue associated with traditional line trimmers by providing dollies or wheeled carriages for support. For example, V. D. Morabit in U.S. Pat. No. 6,862,871 discloses a two-wheel carriage device with an angled mounting bracket for attaching a standard hand-held line trimmer. While this device does reduce the fatigue associated with carrying a hand-held line trimmer, it is not suitable for mowing large swaths of lawn, and rotating the trimmer to the vertical to conduct edge trimming requires loosening of the attachment clamp, rotation of the line trimmer and retightening of the clamp, a time-consuming process.
Two wheel filament line devices that combine mowing and trimming are known. Such an apparatus is disclosed by R. O. Raymond in U.S. Pat. No. 4,703,613, where a horizontal cutting head can be tilted slightly to allow closer cutting near fences and buildings. However, this machine does not allow 90 degree rotation of the cutting head to facilitate edging, nor does it have a third wheel or other device to ensure level and even cutting height for large swath lawn mowing.
The previous problem is addressed by C. B. Pittinger in U.S. Pat. No. 4,077,191 which discloses a filament mower/trimmer in a four-wheel frame. This allows for a more stable and even cutting height for lawn mowing, but suffers from the limitation that since the filament line does not extend past the four wheels it cannot be used to trim close to a fence or building.
Other products and/or publications which may be prior art may include the following: (i) ElecTrim (Models 151590, 158000) trimmer product; (ii) Trim-A-Lawn Weed Blaster product; (iii) U.S. Pat. No. 5,906,051 (“Nannen”); (iv) U.S. Pat. No. 6,442,845 (“Wheeler”); (v) U.S. Pat. No. 5,263,303 (“Stroud”); (vi) U.S. Pat. No. 5,287,683 (“Smith”); (vii) U.S. Pat. No. 6,862,871 (“Morabit”); (viii) U.S. Pat. No. 5,970,694 (“Knox”); (ix) U.S. Pat. No. 5,491,962 (“Sutliff”); (x) U.S. Pat. No. 4,936,886 (“Quillen”); (xi) U.S. Pat. No. 4,688,376 (“Wolfe”); (xii) U.S. Pat. No. 4,442,659 (“Enbusk”); (xiii) U.S. Pat. No. 5,649,413 (“Oostendorp”); (xiv) UK published patent application GB2000672 (“Kalmar”); (xv) German patent related publication number DE2556553 (automated translation); (xvi) U.S. Pat. No. 4,607,431 (“Gay”); and/or (xvii) U.S. Pat. No. 4,227,280 (“Comer”).
It is noted that FIG. 7 of Sutliff discloses an airfoil on its cutting blade. This air foil structure may be useful in conjunction with embodiments of the present invention (discussed below) because the air foil creates a drag on the cutting blade and thereby decreases its kinetic energy.
Description Of the Related Art Section Disclaimer: To the extent that specific publications are discussed above in this Description of the Related Art Section, these discussions should not be taken as an admission that the discussed publications (for example, published patents) are prior art for patent law purposes. For example, some or all of the discussed publications may not be sufficiently early in time, may not reflect subject matter developed early enough in time and/or may not be sufficiently enabling so as to amount to prior art for patent law purposes. To the extent that specific publications are discussed above in this Description of the Related Art Section, they are all hereby incorporated by reference into this document in their respective entirety(ies).